Circuit for actuating electric motors, especially in an electronic typewriter

Abstract

In an electronic typewriter having a printing device of the daisywheel type, the direct current electric motors which control the rotation of the character-carrying element, the movement of the carriage along the various printing positions and the rotation of the platen roller for line spacing are associated with corresponding transducers which detect the angular position thereof, and are actuated by a single integrated circuit connected to a microprocessor by an address and data bus (43). The microprocessor determines, for each of the motors, the angular amplitude of the rotary movement and the time required to cover each of the elementary angular distances, in accordance with a given speed law and addresses with data, including the said time, a plurality of circuit modules (B1, B2, B3) individual to the motors. The modules issue motor command signals (e.g. M11, M21, M31). Checking as between the actual speed and the desired or theoretical speed is effected by the modules of the integrated circuit using the timing signals (e.g. STA 1, STB 1) generated by the transducers connected to the motors. The modules send back interrupt signals (INT 1, INT 2, INT 3) which provide interrupt vectors (46) for the microprocessor, enabling the microprocessor to determine the new data to be sent to the modules.

I claim: 
     
       1. A circuit for actuating at least an electric motor of an electronic typewriter, wherein the typewriter comprises an electric motor having a shaft performing elementary rotary movements; transducer means associated with said motor for generating position signals of impulse type which are indicative of each elementary rotary movement effected by said shaft; a microprocessor for determining a number of said elementary rotary movements to be effected by said shaft in order to attain a given angular displacement; and a circuit module connected with said microprocessor and with said motor and responsive to each of said position signals for controlling the velocity of said shaft for elementary rotary movement of said shaft; wherein said microprocessor also comprises microprocessor time memory means permanently storing a plurality of values of theoretical times TR associated with said number of said elementary movements and read-out means actuatable for reading-out in said circuit module one of said theoretical times, wherein said plurality of values of said theoretical times TR being provided for performing said number of said elementary rotary movements according to a predetermined law of movement of said shaft along with said given angular displacement; and the combination comprising: said circuit module comprises a circuit module memory means for storing a theoretical time signal TT associated with a value of said plurality of values of theoretical times TR read-out from said microprocessor time memory means;   timing means responsive to said position signals for determining an evolving time signal CNT indicative of the interval of time elasping from a last received position signal along one elementary rotary movement;   comparison menas for comparing said evolving time signal CNT with said theoretical time signal TR and generating an equality signal REF when the evolving time signal CNT is equal with the theoretical time signal TR;   logic means responsive to the position signal and to the equality signal REF for actuating said motor to correct the velocity of said shaft during said one elementary rotary movement;   means for generating a corresponding interrupt signal for the microprocessor, at the end of said one elementary rotary movement; and   data addressing means for receiving data processed by said microprocessor in said circuit module, wherein the read-out means of said microprocessor respond to said interrupt signal to generate a new value of said plurality of values of theoretical times TR for another elementary rotary movement following said one elementary rotary movement; and   wherein said logic means accelerates said motor during said one elementary movement independently of any command by said microprocessor if the equality signal REF has been received before said position signal as indicative of the end of said one elementary movement.   
     
     
       2. A circuit according to claim 1, wherein said microprocessor comprises means for storing an effective time signal TE associated with the evolving time signal CNT at the end of said one elementary rotary movement in response to said interrupt signal and means responsive to said effective time signal TE for generating a forcing time TF less than said theoretical time TR and reading-out said effective time into said circuit module, and wherein said logic means cause actuation of said electric motor to accelerate or decelerate, respectively, said shaft during another elementary rotary movement which follows said one elementary rotary movement in response to a new theoretical time TR and said forcing time signal TF as calculated after said one elementary rotary movement. 
     
     
       3. A circuit according to claim 2, wherein said circuit module memory means comprise a first register for storing said theoretical time TR, said timing means comprise a counter actuatable for counting clock pulses in response to the position signal and generating said evolving time signal CNT, and said comparison means comprise a first comparator connected to said first register and said counter for generating said equality signal REF, wherein said circuit module further comprises a second register to store said forcing time TF and a second comparator connected to said second register and said counter and generating another equality signal COR to indicate that the elasped time signal CNT is equal to said forcing time signal TF, wherein said logic means comprise means responsive to said other equality signal COR of said second comparator to hold disabled said motor for a given remaining time, wherein said remaining time is included between said forcing time TF and said theoretical time TR if the equality signal from said first comparator is received before the position signal fromsaid transducer means which is indicative that the theoretical time TR is less than the effective time TE, and wherein said remaining time is included between said forcing time TF and said effective time TE if said position signal from said transducer means is received without any receipt of said equality signal from said first comparator. 
     
     
       4. A circuit according to claim 3, wherein said logic means further provide gate means and flip-flop means connected with said equality signal REF from said first comparator and with said other equality signal COR from said second comparator to accelerate directly said motor during said one elementary movement in response to said equality signal of the first comparator received before receipt of said position signal associated with the said end of said one elementary rotary movement. 
     
     
       5. A circuit according to claim 1, wherein said circuit module holds said electric motor in a disabled status for a given time on the basis of an intermediate count during said one elementary movement and wherein the length of said disabled status for a given time on the basis of an intermediate count during said one elementary movement and wherein the length of said disabled status depends on said theoretical time TR of said elementary movement and given forcing time read-out from the microprocessor. 
     
     
       6. A circuit according to claim 1, wherein said circuit module comprises a register for storing commands received from the microprocessor, and wherein said means for generating a corresponding interrupt signal for the microprocessor comprises a logic network connected with said register and responsive to one of said commands and to said position signal for generating said interrupt signal synchronous with said position signal. 
     
     
       7. A circuit according to claim 1 wherein said circuit actuates other motors, wherein said microprocessor determines said number of elementary rotary movements and said theoretical time TR for the other motors, further comprising other circuit modules substantially similar to said circuit module and wherein all of said circuit modules and the data addressing means are integrated into a single component. 
     
     
       8. A circuit according to claim 7, wherein the typewriter comprises a carriage which is movable parallel to a platen roller and a character-carrying disc mounted rotatably on the carriage, wherein a first of the motors controls the displacement of the carriage, a second of the motors controls the rotary movement of the character-carrying disc, and a third of the motors controls the rotary movement of the platen roller. 
     
     
       9. A circuit according to claim 1, wherein the circuit module memory means comprise a first register and the comparison means comprise a comparator connected to the first register and to a counter actuated by the position signals. 
     
     
       10. A circuit according to claim 1, wherein said circuit actuates other motors, wherein said microprocessor determines said number of elemetary rotary movements and said theoretical time TR for the other motors, further comprising other circuit modules substantially similar to said circuit module, wherein said data addressing means comprise a buffer capable of receiving data and addresses transmitted from the microprocessor, an address register connected to the buffer for receiving the addresses transmitted from the microprocessor and an address decoder connected to the address register and to all of said circuit modules. 
     
     
       11. A circuit according to claim 10, wherein said buffer is also connected to each of said circuit modules for transferring the theoretical time TR and other data to said circuit modules. 
     
     
       12. A circuit according to claim 1, wherein said electric motor is a direct current motor and is powered in a switching mode, wherein a forward or reverse command alternates with a short-circuit or disabling command, and wherein said microprocessor determines the various condition of said motor on the basis of the comparison operations carried out by said comparison means. 
     
     
       13. An electronic circuit for actuating a plurality of electric motors of an office typewriter comprising a microprocessor which is capable of determining for each of the motors the direction of rotation and the angular amplitude required to attain a given angular position and calculating for each rotary movement a number of elementary rotary movements to be effected in order to attain said given angular position and, for each elementary rotary movement, a theoretical time signal TR for performing said elementary rotary movement; a plurality of transducers associated with said motors for generating on a plurality of lines position signals which are indicative of the angular position attained by said motors; and a plurality of circuit modules, wherein each circuit module comprises circuit module memory means for storing the value of said theoretical time signal TR; timing means connected with one line of said plurality of lines and responsive to said position signals for determining an evolving time signal CNT indicative of the interval of time elapsing from the time of receipt of a last position signal along said elementary rotary movement; comparison means for comparing the evolving time signal CNT with the theoretical time signal TR; output means controlled by said comparison means and operative on one of said plurality of electric motors, wherein said comparison means causes said output means to accelerate said one motor independently of any command by the microprocessor if a position signal has not been received in said one line of said plurality of lines before the theoretical time TR; and means for generating a corresponding interrupt signal associated with said position signal received on said one line of said plurality of lines for causing said microprocessor to read-out on said circuit module said theoretical time signal TR and a control signal for controlling the acceleration and deceleration of said motor. 
     
     
       14. A circuit according to claim 13, wherein each of said electric motors is a direct current motor and is powered in a switching mode, wherein each one of said circuit modules further comprises means for generating a corresponding interrupt signal for the microprocessor associated with receipt of said position signal, wherein the control signal of said microprocessor causes said output means to accelerate or brake each of said motors for a forcing time TF less than the theoretical time TR and to hold disabled said each of said motors for a remaining time up to TR, wherein said forcing time TF is associated with the effective time TE of a preceding elementary rotation of said each of said motors and wherein the comparison means of each of said circuit modules cause said output means to hold an associated motor disabled if an associated position signal is received before the theoretical time TR and before any new control signal by said microprocessor.